Acrylic copolymer

Abstract

It is intended to in a liquid-immersion exposure process, simultaneously prevent any degeneration, represented by bridge, etc., of resist film during the liquid-immersion exposure using water and other various liquid-immersion exposure liquids and any degeneration of liquid-immersion exposure liquids per se, and to without increasing of the number of treatment steps, realize enhancing of the post-exposure storage stability of resist film, and to enable forming of a resist pattern of high resolution through liquid-immersion exposure. Use is made of an acrylic copolymer of the general formula: wherein R is a hydrogen atom or methyl; R′ is a hydrogen atom, methyl or C 1 -C 4 hydroxyalkyl; R 1 is a C 1 -C 15 linear, branched or cyclic alkyl with the proviso that the hydrogen atoms of the alkyl may be partially or wholly substituted with fluorine atom or atoms; R 2 is an alicyclic hydrocarbon group; R 3 is a linear hydrocarbon group; and each of l, m, n and o is the mol % of structural unit contained, being in the range of 2 to 60 mol %.

1 . An acrylic copolymerized polymer comprising a constituent unit represented by the following general formula (1): 
     
       
         
         
             
             
         
       
       wherein R is a hydrogen atom or a methyl group; R′ is a hydrogen atom, a methyl group, or a hydroxyalkyl group having 1 to 4 carbon atoms; R 1  is a linear, branched or cyclic alkyl group having 1 to 15 carbon atoms, and a portion or all of hydrogen atoms thereof may be substituted with a fluorine atom; R 2  is an alicyclic hydrocarbon group; R 3  is a chain hydrocarbon group; and l, m, n, and o each representing % by mole of the constituent unit in the polymer, are each 2 to 60% by mole. 
     
   
   
       2 . The acrylic copolymerized polymer according to  claim 1  to be included in a material for forming a resist protective film that is used for forming an upper protective film on a resist film. 
   
   
       3 . The acrylic copolymerized polymer according to  claim 2 , wherein the resist film is to be subjected to a liquid immersion lithography process. 
   
   
       4 . The acrylic copolymerized polymer according to  claim 1 , wherein R′ is a hydroxy alkyl group having 1 to 4 carbon atoms in the above general formula (1). 
   
   
       5 . The acrylic copolymerized polymer according to  claim 1  wherein R 1  is represented by the following general formula (2): 
     
       
         
         
             
             
         
       
       wherein R m  is a linear or branched alkylene group having 1 to 5 carbon atoms, and R f  is an alkyl group having 1 to 15 carbon atoms, and a portion or all of hydrogen atoms thereof are substituted with a fluorine atom. 
     
   
   
       6 . The acrylic copolymerized polymer according to  claim 1 , wherein the constituent unit having R 2  in the above general formula (1) comprises a constituent unit having R 2a  and R 2b  wherein R 2a  is a polycyclic hydrocarbon group, and R 2b  is a monocyclic hydrocarbon group. 
   
   
       7 . The acrylic copolymerized polymer according to  claim 6 , wherein R 2a  is at least one hydrocarbon group selected from a dicyclopentanyl group, an adamantyl group, a norbonyl group, an isobornyl group, a tricyclodecyl group and a tetracyclododecyl group. 
   
   
       8 . The acrylic copolymerized polymer according to  claim 6 , wherein R 2b  is at least one hydrocarbon group selected from a cyclohexyl group, a cyclopentyl group and a cycloheptyl group. 
   
   
       9 . The acrylic copolymerized polymer according to  claim 1 , wherein R 3  is at least one hydrocarbon group selected from a n-butyl group, a n-pentyl group, a 2-ethylhexyl group, and a n-hexyl group.